Electric impulse signaling system



May 25, 1948 R. GRAY v E1BCTRIC IIPULSB SIGNALING SYSTEI WAVE GEPERADR SAW TOOTH HIGH PASS FILTER FIG. I.

TRANSMITTER INVENTOR. RICHARD EDMUND GRN BY Fa f Fl 5; 2. RECEIVER ATT Patented May 25, 1948 UNITED STATES PATENT orrica ELECTRIC IMPULSE SIGNALING SYSTEM Richard Edmund Gray, London, England, as'aignor to International Standard Electric Corporation, New York, N. Y.

. Application December 19, 1941, Serial No. 423,865 In France February 3, 1940 Section 1, Public Law 090, August s, 1946 Patent expires February 3, 1960 6 Claims. .(Cl. 179-1715) are connected is that placed on wire HT. The two grids 5-5 are respectively connected to'the wire HT by adjustable resistances 9-8 in series with fixed resistances ill-i to provide a biasing of the grids. In the biasing connection of the grid is inserted the secondary winding of a transformer II to whose primary terminals is applied the modulation wave, for example a receiving end, onlyone of the two series of rectangular signals or impulses generated by double stability trip devices, which ensures to the sharp impulses derived from these rectangular signals and amplified a, greater amplitude than if the two series of rectangular signals were used for signal-' ing purposes.

Furthermore, both at the transmitting and at the receiving end, means such as choke inductances inserted in the plate circuit of the double stability devices are provided to increase the amplitude of the rectangular signals generated,

hence of the impulse derived from these signals.

The invention will be explained in detail'in the following description given in connection with the accompanying drawing, in which:

Fig. 1 shows a transmitting circuit for impulse signaling of the type defined above, incorporating features of the invention; and

Fig. 2 shows a receiving circuit incorporating features of the invention, suitable particularly for use in conjunction with the transmitting circuit shown in Fig. 1.

With reference to Fig. 1, a double stabillt sudden trip device I in the form of a double triode' is shown with exactly balanced plate, grid and filament circuits. In other words, the filament supply (not shown for greater simplicity of the manner with an electric mid-point connection, while the filaments are heated in a series circuit. (Alternatively, a single filament might be employed.) The plate supply is obtained from the wire +HT by means of two identical circuits comprising, for example, two equal value resistances 22', themselves in series with two choke drawing) is for example provided in well known speech wave. Between the fixed resistance l0 and the adjustable resistance 9 of the connection of the other grid 5 is applied the control voltage of the trip device, as indicated at l2, this control voltage coming, for example, from a saw-tooth 4 oscillation generating circuit.

With such an arrangement, the control voltage applied at i 2 will cause the generation, by the double stability device I ,of rectangular oscillations whose duration will be a function of the instantaneous amplitude of the modulation signal applied at Ii. The rectangular signals coming from the plate 4 increase or decrease the charge on the condenser l which charge has been put there by the high tension supply and which can leak on through the resistance 8'. This charge controls the voltage at the grid of tube 4! and hence the triggering action. The rectangular signals coming from the plate 4' increase ordecrease the charge on the condenser I which charge has been put there'or which leaks oil through the resistance 8, the coil resistance 22, and the rectifier I5. The circuit constituted by the condenser i and the coil 22 converts the rectangular pulse into two-sharp short impulses defining the beginning and the end of the rec- These pulses are applied to an tangular pulse. arrangement comprising the two rectifying elements i5 and i8. Rectifier i5 shunts one of said two sharpshort impulses to ground; rectifier it passes the other of said impulses. passed and shunted depend on the respective polarity. These two rectifying elements are connected in relative polarity opposition with regard to the inductance 22, the currents which they pass flowing over a resistance i8 in the cathode circuit of the amplifying tube II. The amplifying tube It is provided with a grid-cathode circuit comprising a resistance IS in series with a condenser 20 and a resistance 2| connected to ground. from the wire +HT across a resistance 24 connected to ground across a condenser 25.

The output circuit of the amplifying tube It consists as usual of a resistance 26 in shunt be- The pulses The plate voltage of tube i4 is taken the resistance. I The si naling voltage at the terminals of this resistance is applied over a highpass filter 28 to eliminate the low frequency modulation products that may have been amplified, and the output is taken at the terminals of this filter to another amplifying stage which reverses the sense of the impulses which are apment being made individually. Furthermore, the

electrical symmetry of the plate circuit is enhanced by two equal capacities 3 |--3|' connectedin series with a mid-ground connection 32 in shunt to the lower terminals of resistances 2 and 2'. The inductances 3 and 3" produce a partial peaking of the anode currents and increase the amplitude of the rectangular impulses supplied by the trip device 1. Otherwise the device I operates in well known manner as a controlled multi-vibrator.

Moreover, the fact that use is made of only one series of rectangular signals in the output of the double stability device I for obtaining the start and end impulses of the signal-s ensures, upon amplification of said impulses by the tube l4, a much greater amplitude than if the two series of rectangular signals were used and the resultant impulses amplified. v

The impulses transmitted are received by a receiver comprising the usual high and medium frequency stages (not shown), and then are applied to the terminals 40 of the circuit of Fig. 2 and thence across adjustable capacities 4| and 4| to the grids 42 and 42' of a double triode double stability device 43 whose filaments are supplied symmetrically in known suitable manner (not shown) and whose plates 44--44 are interconnected with the grids 42' and 42 in the manner already described with reference to Figure 1. Equal grid biasing resistances 45 and 45' are connected between the grids 42 and 42' and the groundwire 46 while the plates 44 and 44 are connected to the wire +HT through fixed resistances 41 and 41', self-inductances 48 and 48 in parallel with the fixed resistances 49-49 and adjustable resistances |l50' respectively. The

electrical symmetry of this plate supply is here further ensured by two equal condensers 5|5|' connected in series between the ends of the fixed resistances 41-41 with their mid-point grounded at 52.

The trip device 43 will thus supply in its output circuit two series of rectangular pulse signals under the control of the impulses received, once the condensers 4| and 4| have been adjusted to suitable values. One series of these impulses will be grounded directly, over a resistance 53' and a condenser 54' while the impulses of the other series are applied to the resistance 53, of the same value asresistance 53', connected to ground at the common wire 46, over a condenser 54 of the same value as the condenser 54. However, this resistance 53 has an adjustable tap 55 whereby the level of the outgoing impulses can be adjusted to apply them over the resistance 58 to the grid of an amplifying tube 51.

The cathode circuit of this amplifying tube 81 comprises the usual parallel combination con-.

denser BS-resistance 58 to ground while its plate supply is furnished from the wire +H'1 over a fixed resistance one end of which is grounded as shown over a capacity BI and the primary winding of an output transformer 62, this winding being shunted by a resistance 83. The secondary of this output transformer 62 is connected to a receiver such as a telephone receiver (not shown) over a low-pass filter 64 which filter eliminates the high frequencies remaining in the rectangular signal pulses.

At the receiver, as at the transmitter, a greater amplitude of the outgoing impulses will be obtained thanks to the suppression of the positive impulses as also on account of the presence of the choke inductances 4848,'which may consist of two windings of a dust core toroidal coil.

Various modifications and adaptations .can be made in the arrangement described within the scope of the present invention.

What is claimed is:

1. A pulse duration modulating circuit arrangement for producing successive pairs of pulses having a time spacing corresponding to the instantaneous amplitude of a modulating wave, comprising a double stability trigger device, means for generating a control signal wave repetitive at the desired pulse repetition frequency, means to apply said control wave to said device so as to cause one portion of said control wave to cause-said double stability device to assume one condition of stability and to cause another portion of said control wave to place said device in condition for assuming its other condition of stability, a source of modulation, means to apply comprising a pair of electron discharge means arranged as a double stability trigger device, means for generating a control wave repetitive at the desired pulse repetition frequency, means to apply said control wave to a control electrode of one of said electron discharge means so as to cause one portion of said control wave to cause said double stability device to assume one condition of stability and to cause another. portion of said control wave to place said. device in condition for assuming its other condition of stability, a source of modulation, means to apply voltage from said source to a control electrode of the other of said electron discharge means, and means to cause said device to assume its other condition of stability a predetermined time from the time at which it has been conditioned by said second mentioned means, said predetermined time being-controlled by the magnitude of the voltage from said source.

3. A pulse duration modulating circuit arrangement for producing successive pairs of pulses having a time spacing corresponding to the instantaneous amplitude of a, modulating wave according to claim 2 wherein the frequencies in the voltage from said source of modulation are much less than the repetition rate of said control wave.

. 4. A pulse duration modulating circuit arrangement for producing successive pairs of pulses having a time spacing corresponding to the instantaneous amplitude of a modulating wave according to claim 5 wherein said last mentioned means comprises a connection from one anode over a'condenser and a resistance to ground, connection from the other anode over a second condenser and a second resistance to ground, an inductive reactance shunted across said second resistance, a rectifier shunted across said inductive reactance and also across said resistance, and an output circuit connected across said inductive reactance.

5. A pulse modulating arrangement for producing successive pairs of pulses having a time spacing corresponding to the instantaneous amplitude of a modulating wave comprising a pair of electron discharge means connected in a double stability trigger circuit, means for generating a control wave, means for applying said control wave to said trigger circuit so as to cause one portion or said control wave to cause said trigger in saidcontrol wave, and means to cause said trigger circuit to assume its other condition of stability a predetermined time from the time at which it has been conditioned by said second mentioned conditioning means, said predetermined time being controlled by the magnitude of the voltage of said modulation wave.

6. A pulse modulating circuit arrangement according to claim 5 wherein each of said electron discharge means includes an anode, and further comprising a high tension supply connected to each anode, and an inductive choke connected in the lead between said high tension supply and the anode of said trigger circuit to difierentlate the output pulses produced in said trigger circuit.

RICHARD EDMUND GRAY.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 2,061,734 Kell Nov. 24; 1936 2,086,918 Luck July 13, 1937 2,110,438 Cumming-s et al Mar. 8, 1938 2,113,214 Luck Apr, 5, 1938 2,118,156 Burton May 24, 1938 2,234,978 Overbeck Mar. 18, 1941 2,262,838 Deloraine et al. Nov. 18, 1941 2,266,401 Reeves Dec. 16,- 1941 72,07 Reeves Feb. 3, 1942 2,338,512 Harmon Jan. 4, 1944 FOREIGN PATENTS Number Country Date 389,855 Great Britain Mar. 27, 1933 558,343 Great Britain Dec. 31, 1943 

